JP7342712B2 - Light shielding plate, camera unit, electronic device, and manufacturing method of light shielding plate - Google Patents

Description

The present invention relates to a light shielding plate, a camera unit including the light shielding plate, an electronic device including the camera unit, and a method for manufacturing the light shielding plate.

Camera units included in electronic devices such as smartphones include a light shielding plate that functions as an aperture for external light. Since it is easy to mold a light shielding plate having a predetermined shape, resin light shielding plates are often used (see, for example, Patent Document 1). However, because of the light transmittance of the light shielding plate, the resin light shielding plate allows external light to pass through not only the holes through which the external light passes, but also the portions that define the holes. As described above, since light shielding by resin light shielding plates is not sufficient, metal light shielding plates having higher light shielding properties are beginning to be used (for example, see Patent Document 2).

Japanese Patent Application Publication No. 2010-8786 International Publication No. 2016/060198

By the way, when manufacturing metal light shielding plates, a punching process in which a metal plate is punched out using a mold is used because the difficulty of processing is low and it is possible to manufacture many products per unit time. It is used. When processing a metal plate using punching, the surface of the metal plate is cut in order to prevent deformation or distortion of the metal plate when punching the metal plate with a die, and thereby ensure accuracy in the dimensions of the product. It is required to punch out the metal plate along the direction perpendicular to the . As a result, a hole having a side surface extending perpendicularly to the surface of the metal plate is formed in the metal plate in a cross section perpendicular to the surface of the metal plate.

When a camera unit is equipped with a light-shielding plate having such holes, external light that enters the light-shielding plate from a direction that forms an acute angle with the surface of the light-shielding plate is reflected on the side surfaces that define the holes, resulting in It may pass through the hole. The light passing through the hole is received by an image sensor included in the camera unit, and excessive light, such as a ghost or flare, may occur in an image captured by the image sensor. In this way, new problems arise with metal light shielding plates because the light shielding plates are made of metal.

SUMMARY OF THE INVENTION An object of the present invention is to provide a light shielding plate, a camera unit, an electronic device, and a method for manufacturing a light shielding plate that can suppress excessive reflection of light caused by light transmitted through holes.

A light shielding plate for solving the above problem is a metal light shielding plate. The device includes a front surface located on the light incident side, a back surface opposite to the front surface, and a hole penetrating between the front surface and the back surface. The hole has a back opening on the back surface, a first hole having a shape tapering from the back surface toward the front surface, and a front opening larger than the back opening on the front surface, and a first hole having a shape that tapers from the back surface toward the front surface. A second hole having a shape tapering toward the back surface and connected to the first hole is provided. Among the openings of the first hole, the opening on the opposite side to the back opening is a central opening having a circular shape, and the circularity of the central opening is 3 μm or less.

A method for manufacturing a light shielding plate to solve the above problems includes arranging a resist layer on the front and back surfaces of a metal foil, forming a resist mask from the resist layer by exposing and developing the resist layer, and , forming a hole penetrating between the front surface and the back surface by etching the metal foil using the resist mask. Forming the hole includes forming a first hole having a back opening on the back surface and tapering from the back surface toward the front surface, and forming a first hole on the front surface that is larger than the back opening. forming a second hole having a shape tapering from the front surface toward the back surface; and by forming the first hole and the second hole, among the openings of the first hole, the back surface A circular central opening is formed on the opposite side of the opening and has a circularity of 3 μm or less, and the inside of the hole formed first among the first hole and the second hole is formed. forming a hole different from the previously formed hole in a state where the hole is filled with a protective portion that protects the hole.

According to each of the above configurations, since the second hole has a shape that tapers from the front surface to the back surface, light incident on the hole from diagonally above the front surface is directed toward the surface of the light shielding plate at the side surface that partitions the second hole. easily reflected. On the other hand, since the first hole has a shape that tapers from the center opening toward the back surface, some of the light that enters the first hole from the second hole is reflected at the side surface that partitions the first hole. light is restricted. In this way, according to the first hole and the second hole, it is possible to reduce the amount of light reflected on the side surface of the hole.

On the other hand, since the circularity of the central opening is 3 μm or less, the distortion of the central opening, which is the path of light incident on the hole, is suppressed. This prevents the amount of light transmitted from the hole toward the first hole from becoming excessive.
For these reasons, the above configuration can suppress excessive reflection of light caused by light passing through the holes.

In the above-mentioned light shielding plate, when the edge of the central opening is imaged along the radial direction of the central opening with the edge of the central opening in focus, under the imaging condition that the depth of field is 0.4 μm. The maximum width of the light shielding plate in the thickness direction of the light shielding plate in focus may be 2.5 μm or less.

According to the above configuration, since the maximum width of the light shielding plate that can be focused is 2.5 μm or less, the area of the side surface that partitions the hole in the vicinity of the central opening is reduced, and thereby, the area of the side surface that partitions the hole in the vicinity of the central opening is reduced. It is possible to reduce the amount of light reflected on the partitioning side surfaces. As a result, it is possible to reduce the amount of light that is reflected on the side surfaces that define the hole so as to pass through the hole.

In the light shielding plate, the maximum width of the light shielding plate may be larger than 1.0 μm. According to this configuration, since the maximum width of the light shielding plate that is in focus is larger than 1.0 μm, it is possible to suppress deformation in the vicinity of the central opening. This suppresses fluctuations in the amount of light that passes through the light shielding plate through the central opening due to deformation of the light shielding plate.

In the above light shielding plate, the light shielding plate may have a thickness of 10 μm or more and 100 μm or less. According to this configuration, since the thickness of the light shielding plate is 10 μm or more, the warpage of the metal foil for forming the light shielding plate is suppressed from affecting the shape of the light shielding plate, and the thickness of the light shielding plate is When the thickness is 100 μm or less, the accuracy of etching for forming holes can be prevented from decreasing.

In the light shielding plate, the light shielding plate may be made of an iron-nickel alloy or an iron-nickel-cobalt alloy.
In the above light shielding plate, the light shielding plate may be made of invar or super invar.

According to each of the above configurations, it is possible to suppress deformation of the light shielding plate due to a change in the outside temperature, and thereby it is possible to suppress a change in the amount of incident outside light due to a change in the outside temperature. Therefore, it is possible to suppress the occurrence of ghosts and flares due to changes in the amount of incident external light.

A camera unit for solving the above problem includes the light shielding plate and a lens. The light shielding plate is located on the light incident side with respect to the lens, with the back surface and the lens facing each other.

According to the above configuration, compared to the case where the surface of the light shielding plate faces the lens, it is possible to limit the light that passes through the central opening and is reflected on the side surface of the hole, thereby limiting the light that enters the lens. .

In the above camera unit, the diameter of the central opening of the light shielding plate may be smaller than or equal to the effective diameter of the lens. According to this configuration, light passing through the central aperture is prevented from entering outside the effective diameter of the lens. Therefore, unintended light is prevented from entering the image sensor.

An electronic device for solving the above problem includes the camera unit and a housing that supports the camera unit.

According to the present invention, it is possible to suppress excessive reflection of light caused by light transmitted through the holes.

FIG. 2 is a plan view showing the structure of a light shielding plate in one embodiment. FIG. 2 is a cross-sectional view showing the structure of the light shielding plate shown in FIG. 1; FIG. 2 is a schematic diagram for explaining the roundness of the central opening provided in the light shielding plate shown in FIG. 1. FIG. FIG. 3 is a partially enlarged cross-sectional view showing a part of the cross-sectional view shown in FIG. 2; FIG. 2 is an action diagram for explaining the action of the light shielding plate shown in FIG. 1 . FIG. 2 is an action diagram for explaining the action of the light shielding plate shown in FIG. 1 . FIG. 2 is an action diagram for explaining the action of the light shielding plate shown in FIG. 1 . FIG. 3 is a process diagram for explaining a method for manufacturing a light shielding plate. FIG. 3 is a process diagram for explaining a method for manufacturing a light shielding plate. FIG. 3 is a process diagram for explaining a method for manufacturing a light shielding plate. FIG. 3 is a process diagram for explaining a method for manufacturing a light shielding plate. FIG. 3 is a process diagram for explaining a method for manufacturing a light shielding plate. FIG. 3 is a process diagram for explaining a method for manufacturing a light shielding plate. FIG. 2 is a configuration diagram schematically showing the structure of a camera unit.

An embodiment of a light shielding plate, a camera unit, an electronic device, and a method of manufacturing a light shielding plate will be described with reference to FIGS. 1 to 14. Below, a light shielding plate, a method of manufacturing the light shielding plate, a camera unit, and an example will be described in order.

[Light shielding plate]
The light shielding plate will be explained with reference to FIGS. 1 to 7.
As shown in FIG. 1, the metal light shielding plate 10 includes a front surface 10F, a back surface 10R, and a hole 10H. The surface 10F is a surface located on the light incident side. The back surface 10R is the surface opposite to the front surface 10F. The hole 10H penetrates between the front surface 10F and the back surface 10R. The light shielding plate 10 is made of stainless steel, for example, but may be made of a metal other than stainless steel. Note that, in the light shielding plate 10, the front surface 10F, the back surface 10R, and the side surfaces defining the holes 10H are covered with an antireflection film (not shown). The antireflection film has a lower reflectance than the metal forming the light shielding plate 10, and has a function of absorbing a portion of the light irradiated onto the antireflection film. Further, even if the light shielding plate 10 is covered with an antireflection film, reflection of light on the light shielding plate 10 cannot be completely eliminated.

The light shielding plate 10 has a circular shape that corresponds to the shape of the lens that the light shielding plate 10 covers. The hole 10H has a circular shape that corresponds to the shape of the lens that the hole 10H faces.

FIG. 2 shows the structure of the light shielding plate 10 in a cross section perpendicular to the surface 10F of the light shielding plate 10.
As shown in FIG. 2, the hole 10H includes a first hole 10H1 and a second hole 10H2. The first hole 10H1 has a back opening H1R on the back surface 10R, and has a shape that tapers from the back surface 10R toward the front surface 10F. In other words, the first hole 10H1 has a shape that becomes thicker from the front surface 10F toward the back surface 10R. The second hole 10H2 has a front opening H2F on the front surface 10F, which is larger than the back opening H1R. The second hole 10H2 has a shape that tapers from the front surface 10F toward the back surface 10R, and is connected to the first hole 10H1. Among the openings that the first hole 10H1 has, the opening on the opposite side to the back opening H1R is a central opening HC having a circular shape.

In this embodiment, in a cross section taken along a plane perpendicular to the surface 10F, the side surface defining the second hole 10H2 is arc-shaped, and the center of curvature of the side surface defining the second hole 10H2 is located on the outside of the light shielding plate 10. positioned. Moreover, the side surface that partitions the first hole 10H1 is arc-shaped, and the center of curvature of the side surface that partitions the first hole 10H1 is located on the outside of the light shielding plate 10.

In the light shielding plate 10, the diameter of the first hole 10H1 is the first diameter DH1, and the diameter of the second hole 10H2 is the second diameter DH2. The first diameter DH1 is a value set depending on the camera unit in which the light shielding plate 10 is mounted. The first diameter DH1 may be 0.4 mm or more and 1.0 mm or less when the light shielding plate 10 is mounted on a camera unit of a smartphone, for example. Further, the first diameter DH1 may be greater than or equal to 2.0 mm and less than or equal to 7.0 mm when the light shielding plate 10 is mounted on, for example, an in-vehicle camera. The percentage of the first diameter DH1 to the second diameter DH2 (DH1/DH2×100) may be, for example, 80% or more and 99% or less.

When the light shielding plate 10 is mounted on a camera unit installed on the front of a smartphone, a tablet personal computer, or a notebook personal computer, the camera unit often photographs a subject at a close distance. Therefore, although the angle of view becomes larger, the light shielding plate 10 does not need to have a large inner diameter in order for the lens to focus on the subject. Furthermore, it is also difficult to increase the outer diameter of the light shielding plate 10 due to space limitations in which the camera unit is arranged. Therefore, the percentage of the first diameter DH1 to the second diameter DH2 may be 80% or more and 90% or less.

On the other hand, when the light shielding plate 10 is mounted on a vehicle-mounted camera, the vehicle-mounted camera often photographs a subject from a medium to long distance. Therefore, the angle of view becomes smaller, but since the space in which the camera unit is placed is less restricted, the diameter of the lens included in the camera unit becomes larger. Accordingly, in order to collect light in a wide range on the lens, in the light shielding plate 10, the ratio of the first diameter DH1 to the second diameter DH2 may be 90% or more and 99% or less.

Further, when the light shielding plate 10 is mounted on a camera unit installed on the back of a smartphone, the camera unit often photographs a subject from a short distance to a long distance. Therefore, in order to cope with the case where the angle of view becomes large, the ratio of the first diameter DH1 to the second diameter DH2 may be 80% or more and below 90%, and in order to cope with the case where the angle of view becomes small, The ratio of the first diameter DH1 to the second diameter DH2 may be 90% or more and 99% or less.

The thickness T of the light shielding plate 10 may be, for example, 10 μm or more and 100 μm or less. When the thickness of the light shielding plate 10 is 10 μm or more, the effect of warping of the metal foil on the shape of the light shielding plate 10 can be suppressed. In addition, when the thickness of the light shielding plate 10 is 100 μm or less, a decrease in etching accuracy when forming the holes 10H can be suppressed.

FIG. 3 schematically shows the shape of the central opening HC viewed from a viewpoint facing the surface 10F of the light shielding plate 10.
The central opening HC provided in the light shielding plate 10 has a circular shape when viewed from a viewpoint facing the surface 10F of the light shielding plate 10. In this embodiment, the holes 10H provided in the light shielding plate 10 are formed by wet etching the light shielding plate 10. At this time, a first hole 10H1 is formed in the light shielding plate 10, and then a second hole 10H2 is formed, whereby a central opening HC is formed by connecting the second hole 10H2 to the first hole 10H1. be done. The central opening HC formed by such a process tends to have a larger roundness than a hole formed by punching a metal foil.

Roundness is defined in JIS B 0621-1984, "Definition and Representation of Geometric Deviation." As stated in "5.3 Roundness" of the relevant standard, "roundness" means "when a circular shape (C) is sandwiched between two concentric geometric circles, the distance between the two concentric circles is This is the value expressed as the minimum difference (f) between the radii of two circles.

That is, as shown in FIG. 3, a first circle C1 and a second circle C2 having the same center CC are set for the central opening HC. The first circle C1 is a perfect circle located within the area defined by the central opening HC and in contact with the central opening HC. On the other hand, the second circle C2 is a perfect circle located outside the area defined by the central opening HC and in contact with the central opening HC. The first circle C1 and the second circle C2 are set so that the distance between the first circle C1 and the second circle is the minimum. The difference (f) between the radius R1 of the first circle C1 and the radius R2 of the second circle is the roundness. In the light shielding plate 10, the circularity of the central opening HC is 3 μm or less.

FIG. 4 shows a part of the cross-sectional structure of the light shielding plate 10 shown in FIG. 2 in an enlarged manner.
As shown in FIG. 4, under the imaging condition that the depth of field is 0.4 μm, the edge of the central aperture HC is imaged along the radial direction of the central aperture HC with the edge of the central aperture HC in focus. When this happens, the maximum width of the light shielding plate 10 in the thickness direction of the light shielding plate 10 that is in focus is the maximum width WM. That is, the maximum width WM is the thickness of the light shielding plate 10 at a position that is the same distance as the depth of field DF from the edge of the central opening HC along the direction orthogonal to the thickness direction of the light shielding plate 10. . The maximum width WM is 2.5 μm or less. Further, the maximum width WM may be 0.5 μm or more. Furthermore, the maximum width WM may be larger than 1.0 μm.

In the light shielding plate 10, by setting the maximum width of the light shielding plate that is in focus to be 2.5 μm or less, the area of the side surface that partitions the hole 10H in the vicinity of the central opening HC is reduced, and thereby, in the vicinity of the central opening HC, It is possible to reduce the amount of light reflected on the side surfaces defining the hole 10H. As a result, it is possible to reduce the amount of light that is reflected on the side surfaces that define the hole so as to pass through the hole 10H. Furthermore, since the maximum width of the light shielding plate that is in focus is larger than 1.0 μm, it is possible to suppress deformation in the vicinity of the central opening HC. This suppresses fluctuations in the amount of light that passes through the light shielding plate 10 through the central opening HC due to deformation of the light shielding plate 10.

FIG. 5 shows a cross-sectional structure of the light shielding plate 10 in this embodiment. Moreover, FIG. 6 shows the planar structure of the light shielding plate 10 viewed from a viewpoint facing the surface 10F of the light shielding plate 10. On the other hand, FIG. 7 shows a cross-sectional structure in an example in which side surfaces defining holes extend along a direction perpendicular to the surface in a cross section perpendicular to the surface. Note that in FIGS. 5 and 7, for convenience of illustration, the first diameter with respect to the thickness of the light shielding plate is reduced.

As shown in FIG. 5, light entering the light shielding plate 10 from a direction perpendicular to the surface 10F enters the hole 10H through the surface opening H2F formed in the surface 10F. Then, the light that has passed through the hole 10H reaches the lens LN by exiting from the back opening H1R formed in the back surface 10R. On the other hand, in the light shielding plate 10, since the second hole 10H2 has a shape that tapers from the front surface 10F toward the back surface 10R, the light that enters the hole 10H from diagonally above the front surface 10F is transmitted to the side surface that partitions the second hole 10H2. is likely to be reflected toward the surface 10F of the light shielding plate 10.

Further, the light that enters the second hole 10H2 from diagonally above the surface 10F is reflected on the side surface having an arc shape such that the center of curvature is located on the outside of the light shielding plate 10. Therefore, the specularly reflected light having the highest brightness among the reflected lights is reflected along the direction toward the surface 10F of the light shielding plate 10 from the arcuate side surface. Therefore, the amount of light reflected on the side surfaces that partition the hole 10H so as to pass through the hole 10H can be further suppressed.

On the other hand, since the first hole 10H1 has a shape that becomes thicker from the central opening HC toward the back surface 10R, some of the light that has entered the first hole 10H1 from the second hole 10H2 is on the side surface that partitions the first hole 10H1. Light reflected is limited. In addition, in the light shielding plate 10, the side surface defining the first hole 10H1 has an arc shape such that the center of curvature is located on the outside of the light shielding plate 10. Therefore, compared to the case where the side surface that partitions the first hole 10H1 has a linear shape, light that enters the hole from diagonally above the front surface 10F is reflected by the side surface that partitions the hole 10H in the vicinity of the back opening H1R. The amount of light emitted can be reduced. Thereby, it is possible to further reduce the amount of light that is reflected on the side surface that partitions the hole 10H so as to pass through the hole.

Since the first hole 10H1 and the second hole 10H2 forming the hole 10H of the light shielding plate 10 have such a shape, it is possible to suppress the amount of light reflected on the side surface that partitions the hole 10H so as to pass through the hole 10H. It is possible. As a result, excessive reflection of light caused by light transmitted through the hole 10H can be suppressed.

As shown in FIG. 6, light enters the hole 10H of the light shielding plate 10 from the entire circumferential direction of the hole 10H. In order to suppress the polarization of the light incident on the hole 10H in the entire circumferential direction of the hole 10H, the deviation between the shape of the central opening HC, which is the path of the light incident on the hole 10H, and the perfect circle must be small. is preferred. In this respect, since the circularity of the central aperture HC is 3 μm or less, the distortion of the central aperture HC, which is the path of light incident on the hole 10H, is suppressed. In this case, the amount of light transmitted from the second hole 10H2 toward the first hole 10H1 is prevented from becoming excessive. This also makes it possible to suppress excessive reflection of light caused by light passing through the hole 10H.

As shown in FIG. 7, light incident on the light shielding plate 100 from a direction perpendicular to the surface 100F is similar to light incident on the light shielding plate 10 from a direction perpendicular to the surface 10F. It enters the hole 100H through the opening. Then, the light that has passed through the hole 100H reaches the lens LN by exiting from the opening formed in the back surface 100R. On the other hand, a part of the light that enters the surface 100F from obliquely above the surface 100F enters the hole 100H from the opening formed in the surface 100F, and is reflected at the side surface that partitions the hole 100H. Since most of the light incident on the side surface is reflected in the direction of specular reflection, the light incident on the side surface is reflected from the side surface toward the lens LN. As a result, unintended light enters the image sensor through the lens LN.

[Method for manufacturing light shielding plate]
A method of manufacturing the light shielding plate 10 will be described with reference to FIGS. 8 to 13. Each of FIGS. 8 to 13 shows the cross-sectional structure of the metal foil at a specific step in the manufacturing process of the light shielding plate 10. In addition, in FIGS. 8 to 13, for convenience of illustration, the ratio of the second diameter DH2 to the thickness of the metal foil is smaller than that of the actual light shielding plate 10, and the ratio of the first diameter DH1 to the thickness of the metal foil is reduced. is smaller than the actual light shielding plate 10. Further, in FIGS. 8 to 13, for convenience of illustration, the ratio of the first diameter DH1 to the second diameter DH2 is smaller than that of the actual light shielding plate 10. Moreover, in FIGS. 8 to 13, for convenience of explanation, only the steps involved in forming the holes 10H that the light shielding plate 10 has in the process of manufacturing the light shielding plate 10 are shown.

The method for manufacturing the light shielding plate 10 includes arranging a resist layer, forming a resist mask, and forming holes. In arranging the resist layer, the resist layer is arranged on the front surface and the back surface of the metal foil. In forming a resist mask, a resist mask is formed from the resist layer by exposing and developing the resist layer. In forming the hole, a hole penetrating between the front surface and the back surface is formed by etching the metal foil using a resist mask. Hereinafter, the method for manufacturing the light shielding plate 10 will be described in more detail with reference to the drawings.

As shown in FIG. 8, when forming the light shielding plate 10, first, a metal foil 10M for forming the light shielding plate 10 is prepared. The metal foil 10M is, for example, a stainless steel foil, but as described above, it may be a metal foil formed of a metal other than stainless steel. The thickness of the metal foil 10M is 10 μm or more and 100 μm or less. When the thickness of the metal foil 10M is 10 μm or more, the effect of warping of the metal foil 10M on the shape of the light shielding plate 10 can be suppressed. Moreover, when the thickness of the metal foil 10M is 100 μm or less, a decrease in etching accuracy when forming the hole 10H can be suppressed. The thickness of the metal foil 10M is approximately the same as the thickness of the light shielding plate 10 manufactured from the metal foil 10M.

Then, resist layers are placed on the front surface 10MF and the back surface 10MR of the metal foil 10M. The front surface 10MF of the metal foil 10M corresponds to the front surface 10F of the light shielding plate 10, and the back surface 10MR of the metal foil 10M corresponds to the rear surface 10R of the light shielding plate 10. A front resist layer RF is arranged on the front surface 10MF of the metal foil 10M, and a back resist layer RR is arranged on the back surface 10MR of the metal foil 10M. Note that dry film resists may be attached to both the front surface 10MF and the back surface 10MR as resist layers RF and RR. Alternatively, resist layers RF and RR may be formed on both the front surface 10MF and the back surface 10MR using a coating liquid for forming the resist layers RF and RR. The resist layers RF and RR may be formed of a negative type resist or may be formed of a positive type resist.

As shown in FIG. 9, a resist mask is formed from the resist layers by exposing and developing the resist layers RF and RR. More specifically, the surface mask RMF is formed from the surface resist layer RF by exposing and developing the surface resist layer RF. Further, by exposing and developing the back resist layer RR, a back mask RMR is formed from the back resist layer RR. The surface mask RMF has a mask hole RMFh for forming a second hole in the metal foil 10M. The back mask RMR has a mask hole RMRh for forming a first hole in the metal foil 10M.

As shown in FIG. 10, a first hole MH1 having a back opening on the back surface 10MR and tapering from the back surface 10MR toward the front surface 10MF is formed using the back mask RMR formed on the back surface 10MR. Formed into metal foil 10M. The first hole MH1 corresponds to the first hole 10H1 that the light shielding plate 10 has. At this time, the metal foil 10M is etched using an etching solution capable of etching the metal foil 10M. Note that before etching the metal foil 10M, the surface mask RMF is covered with a surface protective film PMF having resistance to etching liquid. The surface protection film PMF may fill the mask hole RMFh of the surface mask RMF, or may only cover the mask hole RMFh. By covering the surface mask RMF with the surface protection film PMF, the front surface 10MF of the metal foil 10M is prevented from being etched at the same time as the back surface 10MR of the metal foil 10M.

Note that when the first hole MH1 is formed by etching the back surface 10MR, it has a depth larger than the distance D between the above-mentioned back surface 10R and the central opening HC in the light shielding plate 10 (see FIG. 4). A first hole MH1 is formed.

As shown in FIG. 11, after forming the first hole MH1, a surface mask RMF formed on the front surface 10MF is used to form a hole that has a surface opening on the front surface 10MF and tapers from the front surface 10MF toward the back surface 10MR. A second hole MH2 having a shape is formed in the metal foil 10M. Thereby, the second hole MH2 is connected to the first hole MH1, thereby forming the central opening MHC. The second hole MH2 corresponds to the second hole 10H2 that the light shielding plate 10 has. Further, the central opening MHC corresponds to the central opening HC that the light shielding plate 10 has.

At this time, similarly to when forming the first hole MH1, the metal foil 10M is etched using an etching solution capable of etching the metal foil 10M. Note that before etching the metal foil 10M, the back mask RMR is removed from the back surface 10MR of the metal foil 10M. Then, before etching the metal foil 10M, the back surface 10MR of the metal foil 10M is covered with a back surface protective film PMR having resistance to the etching solution, and the inside of the first hole MH1 is filled. The back surface protective film PMR is an example of a protective portion. By covering the back surface 10MR of the metal foil 10M with the back surface protective film PMR, it is possible to prevent the back surface 10MR of the metal foil 10M from being etched at the same time as the front surface 10MF of the metal foil 10M.

In the etching of the second hole MH2, the front surface 10MF of the metal foil 10M is etched while the first hole MH1 is filled with the back protective film PMR. Therefore, after the etching of the front surface 10MF reaches the back protection film PMR, the supply of the etching solution to the metal foil 10M is controlled by the back protection film PMR. As a result, even when the thickness of the metal foil 10M ranges over a wide range of 10 μm or more and 100 μm or less, the accuracy of the cross-sectional shape of the second hole MH2 can be improved. On the other hand, if the inside of the first hole MH1 is not filled with the back protective film PMR, when the first hole MH1 and the second hole MH2 are connected and the metal foil 10M is penetrated, the first hole The etching solution leaks toward the back surface 10MR of the metal foil 10M through the connection between MH1 and the second hole MH2. As a result, the accuracy in the shape of the first hole MH1 and the shape of the second hole MH2 deteriorates.

As described above, in the method for manufacturing the light shielding plate 10 in this embodiment, forming the holes 10H includes the following matters.
(A) Forming a first hole MH1 having a back opening on the back surface 10MR of the metal foil 10M and tapering from the back surface 10MR toward the front surface 10MF.
(B) Forming a second hole MH2 having a front opening larger than the back opening on the front surface 10MF and tapering from the front surface 10MF toward the back surface 10MR.
(C) By forming the first hole MH1 and the second hole MH2, among the openings that the first hole MH1 has, the opening on the opposite side to the back opening has a circular center with a circularity of 3 μm or less. Forming an open MHC.
(D) Of the first hole MH1 and the second hole MH2, a hole different from the previously formed hole is formed with a protective portion for protecting the hole being filled in the hole formed first. .

The manufacturing method of the light shielding plate 10 in this embodiment is a manufacturing method that enables the formation of the holes 10H having a shape that can suppress excessive reflection of light caused by light transmitted through the holes 10H. . In this manufacturing method, since the first hole 10H1 (MH1) and the second hole 10H2 (MH2) are formed in sequence, the amount of light incident on the hole 10H is higher than when the holes are formed at once by punching the metal foil 10M. A unique and new problem arises in that it is difficult to control the roundness of the central aperture HC (MHC), which is the light path.

In this respect, by including the above-mentioned (D) as in the manufacturing method described above, these problems are solved and it is possible to form a central opening HC (MHC) with a circularity of 3 μm or less. be.

Furthermore, when forming the second hole MH2 in the metal foil 10M, the second hole MH2 is connected to the vicinity of the center of the first hole MH1 in the thickness direction of the metal foil 10M in a cross section perpendicular to the surface 10MF. It is preferable to form the second hole MH2 as shown in FIG. The second hole MH2 preferably connects to the first hole MH1 at a position within ±1 μm from the center of the first hole MH1 in the thickness direction of the metal foil 10M in a cross section perpendicular to the surface 10MF.

On the other hand, as shown in FIG. 12, in the cross section perpendicular to the front surface 10MF, when the second hole MH2 is connected to the first hole MH1 at the back opening of the first hole MH1, there is no metal in the vicinity of the back opening. The thickness of the foil 10M becomes very thin. Therefore, when the second hole MH2 connects to the first hole MH1, the vicinity of the back opening may be excessively etched, or the degree to which the metal foil 10M is etched varies in the circumferential direction of the back opening. As a result, while the maximum width WM of the light shielding plate 10 described above becomes smaller, the roundness tends to become larger.

On the other hand, as shown in FIG. 13, in the cross section perpendicular to the surface 10MF, when the second hole MH2 is connected to the first hole MH1 near the bottom of the first hole MH1, the maximum width WM of the light shielding plate 10 is Since the size of the metal foil 10M is increased, excessive etching of the metal foil 10M or uneven etching in the vicinity of the back opening can be suppressed. As a result, while the roundness decreases, the maximum width WM of the light shielding plate 10 tends to increase.

On the other hand, according to the method described above with reference to FIG. 11, it is possible to suppress both the increase in the roundness of the central opening HC and the increase in the maximum width WM of the light shielding plate 10. is possible. Thereby, it is possible to suppress excessive reflection of light caused by light passing through the hole 10H, that is, ghost and flare.

Note that after forming the first hole MH1 and the second hole MH2, the front mask RMF is removed from the front surface 10MF, and the back protective film PMR is removed from the back surface 10MR. Further, after the front mask RMF and the back protective film PMR are removed from the metal foil 10M, an antireflection film is formed to cover the front surface 10MF, the back surface 10MR, and the side surfaces that partition the first hole MH1 and the second hole MH2. . As described above, the antireflection film has a lower reflectance than the metal foil 10M and has a function of absorbing a portion of the light incident on the antireflection film.

The antireflection film is, for example, a black film. The antireflection film may be formed on the metal foil 10M using a film forming method such as a sputtering method or a vapor deposition method. Alternatively, the antireflection film may be formed on the metal foil 10M by bringing the metal foil 10M into contact with a liquid for forming the antireflection film.

In the method for manufacturing the light shielding plate 10 described above, it is not necessary to remove the back mask RMR before forming the back protective film PMR. In this case, it is sufficient to form a back protection film PMR that covers the back mask RMR and fills the first hole MH1. Further, the back protection film PMR may be removed from the back surface 10MR together with the back mask RMR after the second hole MH2 is formed by etching the front surface 10MF.

[Camera unit]
The camera unit will be explained with reference to FIG. 14. Note that FIG. 14 schematically shows the configuration of the camera unit.

As shown in FIG. 14, the camera unit 20 includes the above-described light shielding plate 10, lens 21, and image sensor 22. The light shielding plate 10 is located on the light incident side with respect to the lens 21, with the back surface 10R and the lens 21 facing each other. Compared to the case where the surface 10F of the light shielding plate 10 faces the lens 21, it is possible to restrict the light that enters the lens 21 by being reflected at the side surface of the hole 10H after passing through the central opening HC. be.

The diameter of the central opening HC of the light shielding plate 10 may be smaller than or equal to the effective diameter of the lens 21. This prevents light passing through the central aperture from entering outside the effective diameter of the lens. Therefore, unintended light is prevented from entering the image sensor.

The image sensor 22 may be a CCD image sensor or a CMOS image sensor. In the camera unit 20, one light shielding plate 10 and one lens 21 adjacent to the light shielding plate 10 on the optical axis of light passing through the light shielding plate 10 form one lens unit. Camera unit 20 can include multiple lens units.

Such a camera unit 20 is installed in various electronic devices. The electronic device includes the camera unit 20 described above and a housing that supports the camera unit 20. The electronic device may be, for example, a smartphone, a tablet personal computer, a notebook personal computer, or the like.

[Example]
Examples and comparative examples of light shielding plates will be described with reference to Table 1.
A stainless steel plate with a thickness of 25 μm was prepared. Then, after forming a plurality of second holes in the stainless steel plate using a roll-to-roll method, first holes connected to each second hole were formed. As a result, a plurality of light shielding plate precursors having holes including a back opening with a diameter of 493 μm, a front opening with a diameter of 680 μm, and a central opening with a diameter of 490 μm were formed on the stainless steel plate.

Note that the precursor of each light-shielding plate was connected to the non-etched region of the stainless steel plate by a portion in the circumferential direction of the light-shielding plate when viewed from a viewpoint facing the surface of the light-shielding plate. Further, precursors of a plurality of light shielding plates were formed on the stainless steel plate so that the central opening of each light shielding plate was located at a lattice point in a virtual square lattice set on the stainless steel plate.

When manufacturing the light shielding plates of Examples 1 to 3, Comparative Example 1, and Comparative Example 2, the conveyance speed of the stainless steel plate when forming the first holes was set to different values. Specifically, the conveyance speed when manufacturing the light shielding plate of the example was set to a higher speed than the conveyance speed when manufacturing the light shielding plate of the comparative example. In Examples 1 to 3, the transport speed of Example 1 was set to the lowest speed, and the transport speed of Example 3 was set to the highest speed. Further, the conveyance speed of Comparative Example 1 was set to be lower than the conveyance speed of Comparative Example 2.

On the other hand, when manufacturing the light shielding plate of Comparative Example 3, a stainless steel plate having a thickness of 25 μm was prepared. Then, a plurality of light shielding plates each having a hole having a diameter of 490 μm were formed by punching.

[Evaluation method]
In the precursors of a plurality of light shielding plates formed on stainless steel plates, the roundness was calculated for the precursors of 15 columns and 15 rows of light shielding plates. To calculate the roundness, a laser length measuring machine (NEXIV VMZ-R6555, manufactured by Nikon Corporation) and measurement software installed in the apparatus were used.

In addition, among the precursors of a plurality of light shielding plates formed on a stainless steel plate, the precursors of 15 columns and 15 rows of light shielding plates were examined using a confocal laser microscope (VK-X1000Series, manufactured by Keyence Corporation). Significant WM was measured. At this time, a 50x objective lens was attached to the confocal laser microscope. Further, the maximum width WM was measured by observing the side surface with a confocal laser microscope from the direction opposite to the side surface defining the hole, with the edge of the central opening in focus. In a confocal laser microscope, the in-focus range, that is, the depth of field, differs depending on the magnification of the objective lens. Furthermore, since the object is in focus within the depth of field, the maximum width of the light shielding plate in the thickness direction varies depending on the position from the edge of the central aperture. Therefore, the thickness of the light shielding plate at the position where it is actually in focus has a predetermined width. The depth of field of the 50x objective lens is 0.4 μm. Therefore, when the depth of field is 0.4 μm and the edge of the central aperture is in focus, the maximum value of the width of the light shielding plate in the thickness direction of the light shielding plate was defined as the maximum width. That is, the thickness of the light shielding plate at a position separated by the depth of field from the edge of the central opening is the maximum width WM of the light shielding plate.

[Evaluation results]
In the light shielding plates of Examples 1 to 3 and the light shielding plates of Comparative Examples 1 to 3, the roundness measurement results and maximum width measurement results are as shown in Table 1 below. Ta. Note that the roundness and maximum width shown in Table 1 are the maximum values of the 225 light shielding plate precursors that were measured in each Example and each Comparative Example.

Among the light shielding plates of Examples 1 to 3 and the light shielding plates of Comparative Examples 1 to 3, a camera unit was created that included a light shielding plate having the maximum roundness. Then, it was confirmed whether excessive light was reflected in images captured using the camera unit, that is, whether ghosts or flares were occurring.

As Table 1 shows, the maximum roundness value in Example 1 is 2.6 μm, the maximum roundness value in Example 2 is 2.1 μm, and the maximum roundness value in Example 3. The value was found to be 2.5 μm. Further, it was observed that the maximum value of circularity in Comparative Example 1 was 4.0 μm, and the maximum value of circularity in Comparative Example 2 was 3.9 μm.

Further, the maximum value of the maximum width in Example 1 is 1.5 μm, the maximum value of the maximum width in Example 2 is 2.0 μm, and the maximum value of the maximum width in Example 3 is 2.5 μm. was recognized. Further, it was observed that the maximum value of the maximum width in Comparative Example 1 was 0.5 μm, and the maximum value of the maximum width in Comparative Example 2 was 1.0 μm.

Note that, as described above, the light shielding plate of Comparative Example 3 was not evaluated for roundness and maximum width because it was not a light shielding plate formed by etching metal foil.

When the images captured by the camera units equipped with each of the light shielding plates were checked, no ghost or flare was observed in the images captured by the camera units equipped with the light shielding plates of Examples 1 to 3.

On the other hand, ghosts and flares were observed in images captured by camera units equipped with light shielding plates of Comparative Examples 1 to 3. Among Comparative Examples 1 to 3, the light shielding plates of Comparative Example 1 and Comparative Example 2 have circularity exceeding 3 μm, so that excessive light is transmitted through a portion of the hole in the circumferential direction. This is thought to cause ghosts and flares. On the other hand, in the light shielding plate of Comparative Example 3, in the cross section perpendicular to the surface of the light shielding plate, the side surfaces defining the holes are perpendicular to the surface, so that excessive light is reflected to pass through the holes. This is thought to cause ghosts and flares.

As described above, according to one embodiment of the light shielding plate, the camera unit, the electronic device, and the method for manufacturing the light shielding plate, the effects described below can be obtained.
(1) Since the second hole 10H2 has a shape that tapers from the front surface 10F toward the back surface 10R, the light incident on the hole from diagonally above the front surface 10F is transmitted to the surface of the light shielding plate 10 on the side surface that partitions the second hole 10H2. It is likely to be reflected towards 10F. On the other hand, since the first hole 10H1 has a shape that becomes thicker from the center opening HC toward the back surface 10R, the first hole 10H1 is absorbed by the first hole 10H1 out of the light that has entered the first hole 10H1 from the second hole 10H2. Light reflected on the partitioning sides is limited. In this way, according to the first hole 10H1 and the second hole 10H2, it is possible to reduce the amount of light reflected on the side surface of the hole 10H.

(2) Since the circularity of the central opening HC is 3 μm or less, the distortion of the central opening HC, which is the path of the light incident on the hole 10H, is suppressed, and as a result, a part of the central opening HC in the circumferential direction In this case, the amount of light transmitted from the second hole 10H2 toward the first hole 10H1 is prevented from becoming excessive.

(3) By setting the maximum width WM of the light shielding plate 10 that is in focus to be 2.5 μm or less, the area of the side surface that partitions the hole 10H in the vicinity of the central opening HC is reduced, thereby making it possible to reduce the area in the vicinity of the central opening HC. It is possible to reduce the amount of light reflected on the side surfaces defining the hole 10H. As a result, it is possible to reduce the amount of light that is reflected on the side surfaces that define the hole 10H so as to pass through the hole 10H.

(4) Since the maximum width WM of the light shielding plate 10 that is in focus is larger than 1.0 μm, it is possible to suppress deformation in the vicinity of the central opening HC. This suppresses fluctuations in the amount of light that passes through the light shielding plate 10 through the central opening HC due to deformation of the light shielding plate 10.

(5) Since the thickness of the light shielding plate 10 is 10 μm or more, the warping of the metal foil 10M for forming the light shielding plate 10 is suppressed from affecting the shape of the light shielding plate 10, and the light shielding plate 10 By having a thickness of 100 μm or less, the accuracy of etching for forming the holes 10H is prevented from decreasing.

(6) Compared to the case where the surface 10F of the light shielding plate 10 faces the lens 21, it is possible to restrict the light that enters the lens 21 by being reflected on the side surface of the hole 10H after passing through the central opening HC. It is possible.

(7) Light passing through the central aperture HC is prevented from entering outside the effective diameter of the lens 21. Therefore, unintended light is prevented from entering the image sensor 22.

Note that the embodiment described above can be modified and implemented as follows.
[Method for manufacturing light shielding plate]
- When manufacturing the light shielding plate 10, after forming the second hole 10H2 by etching the metal foil 10M, the first hole 10H1 may be formed so as to be connected to the second hole 10H2. In this case, the first hole 10H1 is connected to the second hole 10H2 while the second hole 10H2 is filled with a surface protective film PMF that protects the second hole 10H2 formed before the first hole 10H1. It can be formed as follows. Even in this case, since the hole 10H includes the first hole 10H1 and the second hole 10H2, and the circularity of the central opening HC is 3 μm or less, the effect according to (1) described above can be obtained. It is possible.

[Metal foil]
- The metal foil 10M for forming the light shielding plate 10 is not limited to stainless steel foil, and may be, for example, a metal foil made of an iron-nickel alloy or a metal foil made of an iron-nickel-cobalt alloy. The iron-nickel alloy may be, for example, Invar, and the iron-nickel-cobalt alloy may be, for example, Super Invar. That is, the light shielding plate 10 may be made of an iron-nickel alloy or an iron-nickel-cobalt alloy. Further, the light shielding plate 10 may be made of invar or super invar.

According to the above configuration, the following effects can be obtained.
(8) Deformation of the light shielding plate 10 due to changes in outside temperature can be suppressed, thereby suppressing changes in the amount of incident outside light due to changes in outside temperature. Therefore, it is possible to suppress the occurrence of ghosts and flares due to changes in the amount of incident external light.

- The metal foil 10M for forming the light shielding plate 10 may have a thickness of less than 10 μm, or may have a thickness of more than 100 μm. That is, the light shielding plate 10 may have a thickness of less than 10 μm or more than 100 μm. Even in this case, since the hole 10H includes the first hole 10H1 and the second hole 10H2, and the circularity of the central opening HC is 3 μm or less, the effect according to (1) described above can be obtained. It is possible.

[Light shielding plate]
- The maximum width WM of the light shielding plate 10 may be less than 0.5 μm or more than 2.5 μm. Even in these cases, the effect similar to (1) described above can be achieved by the hole 10H having the first hole 10H1 and the second hole 10H2 and the circularity of the central opening HC being 3 μm or less. You can get it.

10, 100... Light shielding plate 10F, 10MF, 100F... Front surface 10H, 100H... Hole 10H1, MH1... First hole 10H2, MH2... Second hole 10M... Metal foil 10MR, 10R, 100R... Back surface 20... Camera unit 21... Lens 22...Image sensor H1R...back opening H2F...front opening HC, MHC...center opening PMF...surface protective film PMR...back protective film RF...front resist layer RMF...front mask RMFh, RMRh...mask hole RMR...back mask RR...back resist layer

Claims (10)

A metal light shielding plate,
a surface located on the light incidence side;
a back surface that is the opposite surface to the front surface;
a hole penetrating between the front surface and the back surface,
The hole has a back opening on the back surface, a first hole having a shape that gradually tapers from the back surface toward the front surface, and a front opening on the front surface that is larger than the back opening, a second hole having a shape that gradually tapers from the front surface toward the back surface and connected to the first hole,
Among the openings of the first hole, the opening on the opposite side to the back opening is a central opening having a circular shape;
The circularity of the central opening is 3 μm or less,
Under the imaging condition that the depth of field is 0.4 μm, when the edge of the central aperture is imaged along the radial direction of the central aperture with the edge of the central aperture in focus, the The maximum width of the light shielding plate in the thickness direction of the light shielding plate is greater than 1.0 μm and not more than 2.5 μm.
Light blocking plate. In a cross section along a plane perpendicular to the surface, a side surface defining the first hole is arcuate,
The light shielding plate according to claim 1 , wherein in the cross section, a side surface defining the second hole is arcuate . In a cross section taken along a plane perpendicular to the surface, the side surface defining the first hole is arcuate, and the center of curvature of the side surface defining the first hole is located outside the light shielding plate. 1. The light shielding plate according to 1 . The light shielding plate according to any one of claims 1 to 3, wherein the light shielding plate has a thickness of 10 μm or more and 100 μm or less. The light shielding plate according to any one of claims 1 to 4, wherein the light shielding plate is made of an iron-nickel alloy or an iron-nickel-cobalt alloy. The light shielding plate according to claim 5, wherein the light shielding plate is made of invar or super invar. The light shielding plate according to any one of claims 1 to 6,
comprising a lens;
The light shielding plate is located on the light incident side with respect to the lens, with the back surface and the lens facing each other. The camera unit according to claim 7, wherein the diameter of the central opening of the light shielding plate is equal to or smaller than the effective diameter of the lens. A camera unit according to claim 7 or 8,
An electronic device, comprising: a housing that supports the camera unit. arranging a resist layer on the front and back sides of the metal foil;
forming a resist mask from the resist layer by exposing and developing the resist layer; and
forming a hole penetrating between the front surface and the back surface by etching the metal foil using the resist mask,
Forming the hole comprises:
forming a first hole having a back opening on the back surface and having a shape tapering from the back surface toward the front surface;
forming a second hole on the front surface that has a surface opening larger than the back surface opening and has a shape that tapers from the front surface toward the back surface;
By forming the first hole and the second hole, a circular central opening, which is an opening on the opposite side of the back opening of the first hole and has a circularity of 3 μm or less, is formed. to do, and
forming a hole different from the first hole formed first among the first hole and the second hole, the first hole being filled with a protective portion for protecting the hole; Including method for manufacturing a light shielding plate.